1.6.8 Finite-sliding contact between coupled pore pressure-displacement elements

Product: ABAQUS/Standard

Elements tested

CPE4P CPE6MP CPE8P C3D8P C3D8RP C3D10MP C3D20P

CAX4P CAX4RP CAX6MP

Feature tested

Problem description

Two series of tests each consisting of five input files are documented. In the first series a small block is pressed against a larger block that is fixed on the bottom. The smaller block slides horizontally on the larger block according to the prescribed loading and displacement history to test the formulation in large relative sliding. The axisymmetric tests are essentially the same except that the sliding structures are rings; the outer ring is shorter axially than the inner ring, and the sliding is in the axial direction. The mesh shown in Figure 1.6.8–1, which is used to test element CPE4P, is representative of all meshes used in these tests.

In the second series of tests two identical blocks are pressed against each other while no sliding occurs. Fixed boundary conditions for the pore pressure degrees of freedom on the edges away from the contact interface enable the exact calculation of the pore pressure on the contact interface. The mesh shown in Figure 1.6.8–2, which is used to test element CPE4P, is representative of all meshes used in these tests.

Material:

Linear elastic, Young's modulus = 30.0 × 10⁶, Poisson's ratio = 0.0, permeability = 1.0 × 10^–4.

Loading history for sliding tests

Step 1, TRANSIENT:

A downward pressure of 100 is applied on top of the smaller block. For the two- and three-dimensional tests a pore fluid volume flux of 3 × 10^–4 is applied into the smaller block through its upper surface (area is two units). To create a constant flux through the contact interface, a pore fluid volume flux of 1 × 10^–4 is applied out of the larger block lower surface (area is six units). Results should be symmetric about an axis that is parallel to the line joining the centers of the two blocks, and the total pore fluid volume flux through the contact interface should be 6 × 10^–4.

For the axisymmetric tests a pore fluid volume flux of 1 × 10^–4 is applied into the smaller block through its outer surface (area is 12), and a pore fluid volume flux of 1 × 10^–4 is applied out of the larger block inner surface (area is 12). The total pore fluid volume flux through the contact interface should be 3.76 × 10^–3.

Step 2, TRANSIENT:

The top block is made to slide horizontally (1.5 units) over the bottom block. The total pore fluid volume flux through the contact interface should remain 6 × 10^–4 in the two- and three-dimensional tests and 3.76 × 10^–3 in the axisymmetric cases.

Loading history for the nonsliding tests

A downward pressure of 10.0 is applied on top of the upper block. The pore pressure is fixed and equal to 2.0 on the top surface of the upper block. The pore pressure on the bottom surface of the lower block is fixed and equal to 1.0. A coupled pore pressure analysis is conducted, and the pressure on the contact interface should be 1.5 for the two- and three-dimensional tests and 1.375 for the axisymmetric case.